Electronic Screening at Metal Surfaces and the Connection with Physical Phenomena

The screening properties of metal surfaces from an important element in the description of phenomena under investigation in surface physics. The purpose of these notes is to review the basic features of the response of metal electrons to static and dynamic external fields which can be generated by probes such as electrons, atoms, photons, etc. The density functional approach and its time-dependent extension will be used to calculate the screening cloud. Various examples will be given that illustrate the behavior of the density induced at the surface as a function of frequency and momentum and the connection to several observable quantities will be discussed.